Methods and apparatuses for handling uplink (re)transmission in nr-u

ABSTRACT

A user equipment (UE) includes one or more non-transitory computer-readable media containing computer-executable instructions embodied therein, and at least one processor coupled to the one or more non-transitory computer-readable media. The at least one processor is configured to execute the computer-executable instructions to receive a dynamic grant for scheduling a first uplink (UL) resource, determine whether to obtain a first Medium Access Control (MAC) protocol data unit (PDU) for transmission using the first UL resource or to transmit a second MAC PDU before obtaining the first MAC PDU, and transmit the second MAC PDU using the first UL resource when the first UL resource is suitable for transmitting the second MAC PDU.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present disclosure claims the benefit of and priority of provisionalU.S. Patent Application Ser. No. 62/959,736, filed on Jan. 10, 2020,entitled “Method and Apparatus to Handle Uplink Transmission in NR-U”(“the '736 provisional”). The disclosure of the '736 provisional ishereby incorporated fully by reference into the present disclosure forall purposes.

FIELD

The present disclosure is related to wireless communication, and moreparticularly, to methods and apparatuses for handling uplink(re)transmission in NR-Unlicensed (NR-U).

BACKGROUND

New Radio (NR)-based access to unlicensed spectrum has been agreed bythe 3rd Generation Partnership Project (3GPP) as one of the Work Items(WIs) for Release-16. This WI specifies NR enhancements for a singleglobal solution framework for access to unlicensed spectrum whichenables operations of NR in the unlicensed bands (e.g., 5 GHz and 6 GHzbands) taking into account of regional regulatory requirements. TheNR-Unlicensed (NR-U) design should enable fair coexistence betweenalready deployed Wireless-Fidelity (Wi-Fi) generations and NR-U, betweenNR-U and Long Term Evolution-License-Assisted Access (LTE-LAA), betweendifferent NR-U systems, etc.

The NR-U system is to enable the network to allocate, via a singledynamic uplink (UL) grant, multiple PUSCH resources to individual UEs.Since the UEs may need to perform Listen Before Talk (LBT) before eachUL transmission, LBT failures and unsuccessful transmission (e.g., dueto busy channel condition) may affect the transmission of packets usingthe multiple UL resources scheduled by the single dynamic grant. Thus,there exists a need for further improvements in the art.

CITATION LIST

Citation 1: 3GPP TR 38.889 V16.0.0; Study on NR-based access tounlicensed spectrum.

Citation 2: 3GPP TS 37.340 V15.7.0; Multi-connectivity; Overalldescription; Stage-2.

Citation 3: 3GPP TS 38.331 V15.7.0; Radio Resource Control (RRC)protocol specification.

Citation 4: 3GPP TS 38.214 V15.7.0; Physical layer procedures for data.

Citation 5: 3GPP TS 38.321 V15.7.0; Medium Access Control (MAC) protocolspecification.

Citation 6: 3GPP TS 38.212 V15.7.0; Multiplexing and channel coding.

Citation 7: 3GPP TS 38.213 V15.7.0; Physical layer procedures forcontrol.

SUMMARY

The present disclosure is related to methods and apparatuses forhandling uplink (re)transmission in NR-U.

According to a first aspect of the present disclosure, a user equipment(UE) is provided. The UE includes one or more non-transitorycomputer-readable media containing computer-executable instructionsembodied therein, and at least one processor coupled to the one or morenon-transitory computer-readable media. The at least one processor isconfigured to execute the computer-executable instructions to receive adynamic grant for scheduling a first uplink (UL) resource, determinewhether to obtain a first Medium Access Control (MAC) protocol data unit(PDU) for transmission using the first UL resource or to transmit asecond MAC PDU before obtaining the first MAC PDU, and transmit thesecond MAC PDU using the first UL resource if the first UL resource issuitable for transmitting the second MAC PDU.

In an implementation of the first aspect, if the first UL resource isnot suitable for transmitting the second MAC PDU and if the first ULresource is indicated for a new transmission, obtaining the first MACPDU comprises generating the first MAC PDU for the new transmissionusing the first UL resource.

In another implementation of the first aspect, if the first UL resourceis not suitable for transmitting the second MAC PDU and if the first ULresource is indicated for a retransmission, obtaining the first MAC PDUcomprises retrieving the first MAC PDU from a hybrid automatic repeatrequest (HARQ) buffer associated with a HARQ process of the first ULresource for the retransmission using the first UL resource.

In yet another implementation of the first aspect, the first UL resourceis suitable for transmitting the second MAC PDU if at least one of thefollowing conditions is satisfied: the second MAC PDU is generated fortransmission using a second UL resource scheduled by the dynamic grant;the second UL resource is indicated for a new transmission; the secondUL resource is before the first UL resource in a time domain; the sizeof the first UL resource is equal to or greater than the size of thesecond UL resource; the second MAC PDU is not transmitted successfullyon the second UL resource due to a UL Listen-Before-Talk (LBT) failure;and the second UL resource associated with a second hybrid automaticrepeat request (HARQ) process identifier (ID) is different from a firstHARQ ID associated with the first UL resource.

In yet another implementation of the first aspect, the second MAC PDU isstored in a HARQ buffer after being generated, and the HARQ buffer isassociated with a HARQ process of the second UL resource.

In yet another implementation of the first aspect, the at least oneprocessor is further configured to execute the computer-executableinstructions to: obtain the second MAC PDU from the HARQ buffer fortransmission using the first UL resource.

In yet another implementation of the first aspect, the dynamic grantfurther schedules a second UL resource, the first UL resource isimmediately after the second UL resource in a time domain.

In yet another implementation of the first aspect, wherein the first ULresource and the second UL resource are physical uplink shared channel(PUSCH) resources.

In yet another implementation of the first aspect, a size of the firstUL resource is equal to or greater than a size of the second ULresource.

In yet another implementation of the first aspect, the dynamic grant isreceived in downlink control information (DCI).

According to a second aspect of the present disclosure, a method forwireless communication performed by a UE is provided. The methodincludes receiving a dynamic grant for scheduling a first uplink (UL)resource, determining whether to obtain a first Medium Access Control(MAC) protocol data unit (PDU) for transmission using the first ULresource or to transmit a second MAC PDU before obtaining the first MACPDU, and transmitting the second MAC PDU using the first UL resource ifthe first UL resource is suitable for transmitting the second MAC PDU.

In an implementation of the second aspect, if the first UL resource isnot suitable for transmitting the second MAC PDU and if the first ULresource is indicated for a new transmission, obtaining the first MACPDU comprises generating the first MAC PDU for the new transmissionusing the first UL resource.

In another implementation of the second aspect, if the first UL resourceis not suitable for transmitting the second MAC PDU and if the first ULresource is indicated for a retransmission, obtaining the first MAC PDUcomprises retrieving the first MAC PDU from a hybrid automatic repeatrequest (HARQ) buffer associated with a HARQ process of the first ULresource for the retransmission using the first UL resource.

In yet another implementation of the second aspect, the first ULresource is suitable for transmitting the second MAC PDU if at least oneof the following conditions is satisfied: the second MAC PDU isgenerated for transmission using a second UL resource scheduled by thedynamic grant; the second UL resource is indicated for a newtransmission; the second UL resource is before the first UL resource ina time domain; the size of the first UL resource is equal to or greaterthan the size of the second UL resource; the second MAC PDU is nottransmitted successfully on the second UL resource due to a ULListen-Before-Talk (LBT) failure; and the second UL resource associatedwith a second hybrid automatic repeat request (HARQ) process identifier(ID) is different from a first HARQ ID associated with the first ULresource.

In yet another implementation of the second aspect, the second MAC PDUis stored in a HARQ buffer after being generated, and the HARQ buffer isassociated with a HARQ process of the second UL resource.

In yet another implementation of the second aspect, the method furtherincludes obtaining the second MAC PDU from the HARQ buffer fortransmission using the first UL resource.

In yet another implementation of the second aspect, the dynamic grantfurther schedules a second UL resource, the first UL resource isimmediately after the second UL resource in a time domain.

In yet another implementation of the second aspect, the first ULresource and the second UL resource are physical uplink shared channel(PUSCH) resources.

In yet another implementation of the second aspect, a size of the firstUL resource is equal to or greater than a size of the second ULresource.

In yet another implementation of the second aspect, the dynamic grant isreceived in downlink control information (DCI).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are best understood from the followingdetailed description when read with the accompanying drawings. Variousfeatures are not drawn to scale. Dimensions of various features may bearbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates a time-domain relationship between one PDCCH to onePUSCH resource allocation, in accordance with an example implementationof the present disclosure.

FIG. 2 illustrates a time-domain relationship between one PDCCH to twoPUSCHs resource allocation, in accordance with an example implementationof the present disclosure.

FIG. 3 illustrates a flowchart of a method by a UE for an LBT failureand recovery procedure, according to an example implementation of thepresent disclosure.

FIG. 4 illustrates a flowchart of a method by a UE for an LBT failureand recovery procedure, according to an example implementation of thepresent disclosure.

FIG. 5 illustrates a flowchart of a method by a UE for an LBT failureand recovery procedure, according to an example implementation of thepresent disclosure.

FIG. 6 illustrates a diagram for handling (re)transmission on a ULresource scheduled by a multi-TTI UL grant, according to an exampleimplementation of the present disclosure.

FIG. 7 illustrates a flowchart of a method by a UE for handling(re)transmission on a UL resource scheduled by a multi-TTI UL grant,according to an example implementation of the present disclosure.

FIG. 8 illustrates a multi-TTI UL grant that schedules multiple PUSCHresources, in accordance with an example implementation of the presentdisclosure.

FIG. 9 is a block diagram illustrating a node for wirelesscommunication, according to various aspects of the present disclosure.

DESCRIPTION

The acronyms used in the present disclosure are defined as follows.Unless otherwise specified, the acronyms have the following meanings.

Acronym Full Name 3GPP 3^(rd) Generation Partnership Project 5G 5^(th)Generation 5GC 5^(th) Generation Core ACK Acknowledgment BFR BeamFailure Recovery BSR Buffer Status Report BWP Band Width Part CAPCChannel Access Priority Class CBRA Contention Based Random Access CCComponent Carrier CCCH Common Control Channel CE Control Element CG CellGroup COT Channel Occupancy Time C-RNTI Cell Radio Network TemporaryIdentifier CSI Channel State information DC Dual Connectivity DCCHDedicated Control Channel DCI Downlink Control Information DL DownlinkE-UTRAN Evolved Universal Terrestrial Radio Access Network EPC EvolvedPacket Core HARQ Hybrid Automatic Repeat Request LAA Licensed AssistedAccess LBT Listen Before Talk LCP Logical Channel Prioritization LTELong Term Evolution MAC Medium Access Control MCG Master Cell Group MCOTMaximum Channel Occupancy Time MIMO Multi-input Multi-output MN MasterNode NDI New Data Indicator NR New RAT/Radio NR-U New Radio UnlicensedPCell Primary Cell PSCell Primary Secondary Cell PDCCH Physical DownlinkControl Channel PDSCH Physical Downlink Shared Channel PDU Protocol DataUnit PHY Physical PHR Power Head Room PRACH Physical Random AccessChannel PUCCH Physical Uplink Control Channel PUSCH Physical UplinkShared Channel RA Random Access RAN Radio Access Network RAR RandomAccess Response RLF Radio Link Failure RRC Radio Resource Control SCellSecondary Cell SCG Secondary Cell Group SpCell Special Cell SRScheduling Request SRB Signaling Radio Bearer SRS Sounding ReferenceSignal TAG Timing Advance Group TB Transport Block TBS Transport BlockSize TDD Time Division Duplex TDRA Time Domain Resource Allocation TRTechnical Report TS Technical Specification TX Transmission UE UserEquipment UCI Uplink Control Information UL Uplink WG Working Group WIWorking Item

The following description contains specific information related toimplementations of the present disclosure. The drawings and theiraccompanying detailed description are merely directed toimplementations. However, the present disclosure is not limited to theseimplementations. Other variations and implementations of the presentdisclosure will be obvious to those skilled in the art.

Unless noted otherwise, like or corresponding elements among thedrawings may be indicated by like or corresponding reference numerals.Moreover, the drawings and illustrations in the present disclosure aregenerally not to scale and are not intended to correspond to actualrelative dimensions.

For the purpose of consistency and ease of understanding, like featuresmay be identified (although, in some examples, not illustrated) by thesame numerals in the drawings. However, the features in differentimplementations may be differed in other respects and shall not benarrowly confined to what is illustrated in the drawings.

The phrases “in one implementation,” or “in some implementations,” mayeach refer to one or more of the same or different implementations. Theterm “coupled” is defined as connected whether directly or indirectlythrough intervening components and is not necessarily limited tophysical connections. The term “comprising” means “including, but notnecessarily limited to” and specifically indicates open-ended inclusionor membership in the so-described combination, group, series orequivalent. The expression “at least one of A, B and C” or “at least oneof the following: A, B and C” means “only A, or only B, or only C, orany combination of A, B and C.”

The terms “system” and “network” may be used interchangeably. The term“and/or” is only an association relationship for describing associatedobjects and represents that three relationships may exist such that Aand/or B may indicate that A exists alone, A and B exist at the sametime, or B exists alone. The character “/” generally represents that theassociated objects are in an “or” relationship.

For the purposes of explanation and non-limitation, specific detailssuch as functional entities, techniques, protocols, and standards areset forth for providing an understanding of the disclosed technology. Inother examples, detailed description of well-known methods,technologies, systems, and architectures are omitted so as not toobscure the description with unnecessary details.

Persons skilled in the art will immediately recognize that any networkfunction(s) or algorithm(s) disclosed may be implemented by hardware,software or a combination of software and hardware. Disclosed functionsmay correspond to modules which may be software, hardware, firmware, orany combination thereof.

A software implementation may include computer-executable instructionsstored on a computer-readable medium such as memory or other types ofstorage devices. One or more microprocessors or general-purposecomputers with communication processing capability may be programmedwith corresponding executable instructions and perform the disclosednetwork function(s) or algorithm(s).

The microprocessors or general-purpose computers may includeApplications Specific Integrated Circuitry (ASIC), programmable logicarrays, and/or using one or more Digital Signal Processor (DSPs).Although some of the disclosed implementations are oriented to softwareinstalled and executing on computer hardware, alternativeimplementations implemented as firmware or as hardware or as acombination of hardware and software are well within the scope of thepresent disclosure. The computer readable medium includes but is notlimited to Random Access Memory (RAM), Read Only Memory (ROM), ErasableProgrammable Read-Only Memory (EPROM), Electrically ErasableProgrammable Read-Only Memory (EEPROM), flash memory, Compact DiscRead-Only Memory (CD-ROM), magnetic cassettes, magnetic tape, magneticdisk storage, or any other equivalent medium capable of storingcomputer-readable instructions.

A radio communication network architecture such as a Long Term Evolution(LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Prosystem, or a 5G NR Radio Access Network (RAN) typically includes atleast one base station (BS), at least one UE, and one or more optionalnetwork elements that provide connection within a network. The UEcommunicates with the network such as a Core Network (CN), an EvolvedPacket Core (EPC) network, an Evolved Universal Terrestrial RAN(E-UTRAN), a 5G Core (5GC), or an internet via a RAN established by oneor more BSs.

A UE may include but is not limited to a mobile station, a mobileterminal or device, or a user communication radio terminal. The UE maybe a portable radio equipment that includes but is not limited to amobile phone, a tablet, a wearable device, a sensor, a vehicle, or aPersonal Digital Assistant (PDA) with wireless communication capability.The UE is configured to receive and transmit signals over an airinterface to one or more cells in a RAN.

The BS may be configured to provide communication services according toat least a Radio Access Technology (RAT) such as WorldwideInteroperability for Microwave Access (WiMAX), Global System for Mobilecommunications (GSM) that is often referred to as 2G, GSM Enhanced Datarates for GSM Evolution (EDGE) RAN (GERAN), General Packet Radio Service(GPRS), Universal Mobile Telecommunication System (UMTS) that is oftenreferred to as 3G based on basic wideband-code division multiple access(W-CDMA), high-speed packet access (HSPA), LTE, LTE-A, evolved LTE(eLTE) that is LTE connected to 5GC, NR (often referred to as 5G),and/or LTE-A Pro. However, the scope of the present disclosure is notlimited to these protocols.

The BS may include but is not limited to a node B (NB) in the UMTS, anevolved node B (eNB) in LTE or LTE-A, a radio network controller (RNC)in UMTS, a BS controller (BSC) in the GSM/GERAN, an ng-eNB in an EvolvedUniversal Terrestrial Radio Access (E-UTRA) BS in connection with 5GC, anext generation Node B (gNB) in the 5G-RAN, or any other apparatuscapable of controlling radio communication and managing radio resourceswithin a cell. The BS may serve one or more UEs via a radio interface.

The BS is operable to provide radio coverage to a specific geographicalarea using a plurality of cells forming the RAN. The BS supports theoperations of the cells. Each cell is operable to provide services to atleast one UE within its radio coverage.

Each cell (often referred to as a serving cell) provides services toserve one or more UEs within its radio coverage such that each cellschedules the DL and optionally uplink (UL) resources to at least one UEwithin its radio coverage for DL and optionally UL packet transmissions.The BS can communicate with one or more UEs in the radio communicationsystem via the plurality of cells.

A cell may allocate SL resources for supporting Proximity Service(ProSe) or Vehicle to Everything (V2X) service. Each cell may haveoverlapped coverage areas with other cells.

As discussed previously, the frame structure for NR supports flexibleconfigurations for accommodating various next generation (e.g., 5G)communication requirements such as Enhanced Mobile Broadband (eMBB),Massive Machine Type Communication (mMTC), and Ultra-Reliable andLow-Latency Communication (URLLC), while fulfilling high reliability,high data rate and low latency requirements. The OrthogonalFrequency-Division Multiplexing (OFDM) technology in the 3rd GenerationPartnership Project (3GPP) may serve as a baseline for an NR waveform.The scalable OFDM numerology such as adaptive sub-carrier spacing,channel bandwidth, and Cyclic Prefix (CP) may also be used.

Two coding schemes are considered for NR, specifically Low-DensityParity-Check (LDPC) code and Polar Code. The coding scheme adaption maybe configured based on channel conditions and/or service applications.

When a transmission time interval (TTI) of a single NR frame includes DLtransmission data, a guard period, and UL transmission data, therespective portions of the DL transmission data, the guard period, andthe UL transmission data may be configured based on the network dynamicsof NR. SL resources may also be provided in an NR frame to support ProSeservices or V2X services.

Example description of some selected terms used in this disclosure aregiven below.

Primary Cell (PCell): For dual connectivity (DC) operation, PCell is themaster cell group (MCG) cell, operating on the primary frequency, inwhich the UE either performs the initial connection establishmentprocedure or initiates the connection re-establishment procedure.

Primary SCG Cell (PSCell): For DC operation, PSCell is the secondarycell group (SCG) cell in which the UE performs random access whenperforming the Reconfiguration with Sync procedure.

Special Cell: For DC operation the term Special Cell (SpCell) refers tothe PCell of the MCG or the PSCell of the SCG, otherwise the termSpecial Cell refers to the PCell.

Secondary Cell: For a UE configured with carrier aggregation (CA), acell providing additional radio resources on top of Special Cell.

Serving Cell: For a UE in RRC_CONNECTED not configured with CA/DC, thereis only one serving cell, which may be referred to as the primary cell.For a UE in RRC_CONNECTED configured with CA/DC, the term “servingcells” may be used to denote the set of cells including the SpCell(s)and all secondary cells.

Listen Before Talk (LBT) is a feature available in Wi-Fi that allowscoexistence with other Wi-Fi nodes. LBT is a mechanism by which anequipment applies clear channel assessment (CCA) before using thechannel. The 3rd Generation Partnership Project (3GPP) chose to specifya conservative LBT scheme similar to what Wi-Fi nodes use in order toensure coexistence of Licensed Assisted Access (LAA) with Wi-Fi. LAAuses carrier aggregation in DL to combine LTE in the unlicensed spectrum(e.g., 5 GHz) with LTE in the licensed band. In NR, LBT may be alsorequired prior to any transmission when operating on the unlicensedspectrum.

In an unlicensed spectrum, a UE may perform channel access beforeperforming a transmission in order to make sure that there is no otherdevice occupying the channel where the transmission is intended to beperformed. For channel access mechanism in NR-U operations, the LTE-LAALBT mechanism may be adopted as the baseline for 5 GHz band and as thestarting point of the design for 6 GHz band. At least for bands whereabsence of Wi-Fi cannot be guaranteed (e.g., by regulation), LBT may beperformed in units of 20 MHz. In general, there are 4 LBT categories.The introduction of each LBT category may be found below. For NR-Uoperations, a UE may perform LBT using one of the 4 LBT categoriesbefore performing an UL transmission for different transmissions in aCOT (as defined below) and different channels/signals to be transmitted.Specifically, a UE may perform LBT using different LBT categories beforeperforming PRACH, PUCCH, PUSCH and SRS transmissions.

Category 1: Immediate Transmission after a Short Switching Gap

This may be used for a transmitter to immediately transmit after aswitching gap inside a COT. More specifically, the switching gap fromreception to transmission is to accommodate the transceiver turnaroundtime and is no longer than 16 μs.

Category 2: LBT without Random Back-Off

The duration of time that the channel (where transmission is intended tobe performed) is sensed to be idle before the transmitting entitytransmits is deterministic.

Category 3: LBT with Random Back-Off with a Contention Window of FixedSize

The LBT procedure has the following procedure as one of its components.The transmitting entity draws a random number N within a contentionwindow. The size of the contention window is specified by the minimumand maximum value of N. The size of the contention window is fixed. Therandom number N is used in the LBT procedure to determine the durationof time that the channel (where transmission is intended to beperformed) is sensed to be idle before the transmitting entity transmitson the channel.

Category 4: LBT with Random Back-Off with a Contention Window ofVariable Size

The LBT procedure has the following as one of its components. Thetransmitting entity draws a random number N within a contention window.The size of contention window is specified by the minimum and maximumvalue of N. The transmitting entity can vary the size of the contentionwindow when drawing the random number N. The random number N is used inthe LBT procedure to determine the duration of time that the channel(where transmission is intended to be performed) is sensed to be idlebefore the transmitting entity transmits on the channel.

The transmission may be performed by a UE only if the LBT is successful,for example, as explained in each of the LBT categories discussed above.Moreover, the maximum continuous transmission time (upon successful LBT)may be predetermined by a COT value. Based on the concept of LBTmechanism, RAN Working Group 2 (WG2) has agreed to assume that theconfigured grant timer, which corresponds to the HARQ process of a PUSCHresource of a configured uplink grant is not (re)started if transmissionis not performed on a PUSCH resource due to an LBT failure (e.g., LBT isnot successful). RAN WG2 also assumes that a pending transport block(TB), which has not been transmitted on a configured uplink grantresource due to an LBT failure, may be (re)transmitted in a (subsequent)configured uplink grant resource (with the same HARQ process).

NR Radio Access operating in Unlicensed Spectrum can operate in a PCell,an SCell, or a PSCell. In stand-alone mode, all cells are in unlicensedspectrum. In another scenario, the NR-U SCells may be operated inunlicensed spectrum whilst the PCell is operated in licensed spectrum.An NR-U SCell may or may not be configured with UL resources. TheDC-type of operation can be configured either with an E-UTRAN node(connected to EPC or 5GC) as a master node (MN) or with an NR node, asdescribed in Citation 2.

gNBs and UEs may apply LBT before performing a transmission (e.g., a ULor DL transmission) on NR-U cells. When LBT is applied, the transmitter(e.g., a gNB or a UE) listens/senses the channel to determine whetherthe channel is idle or busy. The transmitter may perform transmissiononly if the channel is sensed idle.

LBT may be considered successful if the channel is sensed to be idle(e.g., the power detected by a UE, which intends to perform a ULtransmission, is less than a predetermined/configured power threshold)for a predetermined/configured duration of time during an LBT procedure,if LBT category 2/3/4 is performed. LBT may be considered successful ifthe UE performs LBT category 1. Otherwise, an LBT failure may beconsidered. The MAC entity of the UE may receive an LBT failureindication from the PHY layer of the UE upon one/multiple LBTfailure(s). The transmission may be performed by a UE only if the LBT issuccessful (e.g., as explained under each LBT category as shown above).Moreover, the maximum continuous transmission time (upon successful LBT)may be predetermined by a COT value.

In various implementations of the present disclosure, the term “UL LBT”may be referred to an LBT procedure performed by the UE before an ULtransmission. The term “DL LBT” may be referred to an LBT procedureperformed by the network before an DL transmission.

Multi-Transmit Time Interval (Multi-TTI) UL Grant

Since a UE may need to perform LBT independently before each ULtransmission, the chances of LBT failures and unsuccessfultransmissions, due to busy channel condition, are inevitable. To reducethe impact of LBT failures and unsuccessful transmissions, the NR-Usystem enables the network to allocate, via a single dynamic grant,multiple PUSCH resources to individual UEs. Such a grant may be referredto as a multi-TTI UL grant in the present disclosure. A UE may initiatetransmission of multiple TBs on multiple PUSCH resources scheduled by asingle multi-TTI UL grant from a time instance where LBT succeeds untilthe last PUSCH resource allocated by the same multi-TTI UL grant. As aresult, the number of LBT operations and the impact from LBT failuresmay be reduced.

The network may configure a PUSCH TDRA list (e.g., via apusch-TimeDomainAllocationList-r16 IE) to a UE via RRC signaling. ThePUSCH TDRA list may contain one or more rows.

In one implementation, a row of the PUSCH TDRA list may include atime-domain relationship between one PDCCH and one PUSCH resourceallocation. This row may include a parameter, k2, to indicate an offset(e.g., in number of slots/symbols) between the PDCCH and the PUSCHresource allocation in the time domain. Additionally, this row mayinclude a parameter, startSymbolAndLength. The startSymbolAndLengthvalue may be mapped to the starting symbol (S) of the PUSCH resourceallocation on the slot/symbol derived from k2, as well as the length (L)(in number of slots/symbols) of the PUSCH resource allocation in thetime domain.

FIG. 1 illustrates a time-domain relationship between one PDCCH to onePUSCH resource allocation, in accordance with an example implementationof the present disclosure. As illustrated in FIG. 1, a PDCCH is schedulein slot 0. The value of k2 (with a value of 1) is used to indicate anoffset (e.g., in number of slots or symbols) between the PDCCH resourceand the PUSCH resource. Additionally, a startSymbolAndLength value isindicated to the UE. The UE may derive the value of starting symbol andlength (e.g., in number of symbols) from the startSymbolAndLength. Inthe present implementation, the derived starting symbol and length are 7and 5, respectively. That is, the PUSCH resource is scheduled in slot 1(k2=1) at symbol 7 (S=7), and has a duration of 5 symbols (L=5).

In another implementation, a row of the PUSCH TDRA list may include atime-domain relationship between one PDCCH and multiple PUSCH resourceallocations (e.g., that are contiguous in the time domain). This row mayinclude a parameter, k2, to indicate an offset (in number ofslots/symbols) between the PDCCH and the (earliest) PUSCH resourceallocation in the time domain. Additionally, this row may include morethan one startSymbolAndLength value (e.g., up to 8 startSymbolAndLengthvalues). Each startSymbolAndLength value may correspond to one PUSCHresource allocation. For instance, if startSymbolAndLength A correspondsto PUSCH resource A, the starting symbol (S) and the length (L) (innumber of slots/symbols) of PUSCH resource A may be derived fromstartSymbolAndLength A.

FIG. 2 illustrates a time-domain relationship between one PDCCH to twoPUSCHs resource allocation, in accordance with an example implementationof the present disclosure. As illustrated in FIG. 2, a PDCCH is schedulein slot 0, and PUSCH 1 and PUSCH 2 are scheduled in slot 1. The value ofk2 (with a value of 1) is used to indicate an offset (e.g., in number ofslots or symbols) between the PDCCH resource and PUSCH 1 (e.g., theearliest PUSCH resource allocation in the time domain). Additionally, 2startSymbolAndLength values are included in this row, namelystartSymbolAndLength_1 and startSymbolAndLength_2. ThestartSymbolAndLength_1 may be used to derive a starting symbol (S) and alength (L) (in number of symbols) of PUSCH 1. The startSymbolAndLength_2may be used to derive a starting symbol (S) and a length (L) (e.g., innumber of symbols) of PUSCH 2. As shown in FIG. 2, the derived startingsymbol of PUSCH 1 is 3 (S=3) and the length of PUSCH 1 is 5 (L=5). Thederived starting symbol of PUSCH 2 is 8 (S=8) and the length of PUSCH 2is 6 (L=6).

Subsequently, the network may signal a multi-TTI UL grant to the UE. Themulti-TTI UL grant may be signaled on a PDCCH. The bit field (e.g., TDRAfield) of this multi-TTI UL grant may be used to indicate which row ofthe earlier configured PUSCH TDRA list should be applied by the UE.Based on the row as indicated by the multi-TTI UL grant, the UE mayapply the k2 and startSymbolAndLength(s) values from the indicated rowto determine the time-domain offset between the PDCCH where themulti-TTI UL grant is received, as well as the starting symbol(s) andlength(s) of the corresponding PUSCH resource allocation(s).

A multi-TTI UL grant may use the same DCI format as a dynamic grant thatschedules a single PUSCH resource (e.g., DCI format 0-1). Moreover, CRCbits of a multi-TTI UL grant may be scrambled by the C-RNTI of thereceiving UE (which is the same for a dynamic grant that schedules asingle PUSCH resource). However, the bit field (i.e., TDRA field) of amulti-TTI UL grant may only indicate a specific row of the earlierconfigured PUSCH TDRA list. Here, the specific row may be referred to asa row that includes the time-domain relationship between one PDCCH andmultiple PUSCH resource allocations, e.g., a row which includes one k2and more than one startSymbolAndLength values.

The PUSCH resources scheduled or allocated by a multi-TTI UL grant mayhave different HARQ process IDs. For example, the DCI field of amulti-TTI UL grant may indicate only the HARQ process ID of the earliestPUSCH allocation in the time domain. The default HARQ process IDs forsubsequent PUSCH(s) are then incremented by one in the scheduled order(with modulo operation if needed). For example, if a multi-TTI UL grantallocates 3 PUSCH resources (e.g., PUSCH 1, PUSCH 2, and PUSCH 3 in thescheduled order), the DCI field of this multi-TTI UL grant may onlyindicate the HARQ process ID of PUSCH 1. If the indicated HARQ processID of PUSCH 1 is j, the HARQ process IDs of PUSCH 2 and PUSCH 3 are j+1and j+2, respectively, which may be derived by the UE itself.

The NDI may be explicitly indicated for each PUSCH resource scheduled bya multi-TTI UL grant. The network may indicate, via a single multi-TTIUL grant, PUSCH resource(s) for new transmission (e.g., the NDI for theHARQ process of the PUSCH resource for new transmission may have beentoggled compared to the value of previous received transmission with thesame HARQ process) and/or PUSCH resource(s) for retransmission (e.g.,the NDI for the HARQ process of the PUSCH resource for retransmissionmay not have been toggled compared to the value of previous receivedtransmission with the same HARQ process).

When a UE receives a multi-TTI UL grant that indicates multiple PUSCHresource allocations, the UE may perform LBT before transmission on anallocated PUSCH resource. However, instead of being required to performLBT for each allocated PUSCH resource independently, a UE may initiatethe transmission on multiple PUSCHs from the point in time where LBTsucceeds until the last PUSCH resource allocated by the same multi-TTIUL grant. In contrast, when LBT fails (e.g., a UE receives an LBTfailure indication) before transmission on a PUSCH resource, the UE maymap the generated TB for the corresponding PUSCH resource to a differentHARQ process. In another word, if LBT fails (e.g., a UE receives an LBTfailure indication) before transmission on a PUSCH scheduled by amulti-TTI UL grant, the UE may transmit the generated TB, which wasintended for transmission on this PUSCH, in a different PUSCH resource(scheduled by the same multi-TTI UL grant) that associates with adifferent HARQ process ID. In one example, a UE may receive a multi-TTIUL grant from the network allocating PUSCH 1. Consequently, if the UEfails to perform transmission on PUSCH 1 due to LBT failure (e.g., theUE receives an LBT failure indication before the PUSCH 1 transmission),the UE may transmit the generated TB, which was intended to betransmitted on PUSCH 1, on another PUSCH resource (scheduled by the samemulti-TTI UL grant) that associates with a different HARQ process ID.

LBT Failure and Recovery Mechanism

In the present implementation, a counter (LBT_COUNTER), a timer(lbt-FailureDetectionTimer), and a threshold(lbt-FailureInstanceMaxCount) may be introduced to a UL LBT failuremechanism. In addition, the LBT_COUNTER, lbt-FailureDetectionTimer, andlbt-FailureInstanceMaxCount may be configured/maintained perBWP/cell/CG/subset of a CG. The LBT_COUNTER may be initially set to zeroupon (re)configuration and may be incremented by one by the UE when a ULLBT failure happens or when an LBT failure indication is received fromthe PHY layer. Specifically, the UL LBT failure may be caused by any (orspecific) UL transmission type. For example, the LBT_COUNTER may beincremented by one when any (or specific) type of UL transmissionscannot be performed due to the detection of a UL LBT failure. In oneexample, the LBT_COUNTER may be incremented by one for each UL LBTfailure(s) detected by the UE.

The lbt-FailureDetectionTimer may be configured by the network to theUE. It may be (re)started when any (or specific) type of UL transmissioncannot be performed due to a UL LBT failure. Alternatively, thelbt-FailureDetectionTimer may be (re)started by the UE whenever theLBT_COUNTER is incremented. The LBT_COUNTER may be reset (e.g., set tozero) when the lbt-FailureDetectionTimer expires.

If the LBT_COUNTER (maintained at a serving cell) reaches thelbt-FailureInstanceMaxCount, it implies that consistent UL LBT failuresare detected (on an UL BWP of the serving cell). Consequently, an LBTrecovery procedure may be initiated by the UE. The LBT recoveryprocedure may be performed in different ways depending on which (UL BWPand/or) serving cell the (consistent) UL LBT failures are detected.

In one implementation, if consistent UL LBT failures are detected on aBWP of a PCell (e.g., the LBT_COUNTER reacheslbt-FailureInstanceMaxCount for the corresponding UL BWP of the PCell),a PCell LBT recovery procedure may be initiated, which involvestriggering of consistent UL LBT failures for the corresponding UL BWPand initiation of an RA procedure on another BWP (on the PCell)configured with PRACH resources (e.g., UE-initiated BWP switching to aBWP configured with PRACH occasion), and for which consistent UL LBTfailures has not been triggered. Additionally, an LBT failure MAC CE(which identifies the failed Cell and/or BWP) may be reported to thenetwork as part of the PCell LBT recovery procedure (e.g., on a PUSCHscheduled by an UL grant from RAR). However, if consistent UL LBTfailures have been triggered on all of the BWPs (or aBWP_declaration_counter has reached a configuredBWP_declaration_threshold, as described below) on the PCell withconfigured PRACH resources (e.g., PRACH occasion), an RLF may betriggered as described in Citation 3.

FIG. 3 illustrates a flowchart 300 of a method by a UE for an LBTfailure and recovery procedure, according to an example implementationof the present disclosure. As shown in FIG. 3, in action 302, the UE maydetect consistent UL LBT failures on a BWP (BWP_(i)) on a serving cell(e.g., a PCell). For example, the LBT counter maintained for thisserving PCell reaches the MaxLBT threshold. In action 304, the UE maytrigger consistent UL LBT failures of the BWP_(i) on the PCell. Inaction 306, the UE may determine whether the consistent UL LBT failureshave been triggered in all UL BWPs with PRACH resources on the servingPCell.

In action 308, if the consistent UL LBT failures have not been triggeredin all UL BWPs with the PRACH resources on the serving PCell, the UE mayswitch to a new BWP with PRACH resources on the serving PCell and forwhich consistent UL LBT failures have not been triggered. The UE mayinitiate a random access (RA) procedure on the new BWP, and report theLBT failure using a MAC CE (e.g., LBT failure MAC CE) in the new BWPduring the RA procedure. The UE may also re-initialize any suspendedconfiguration(s) on the new UL BWP. The flowchart 300 may then proceedfrom action 308 to action 302.

In action 310, if the consistent UL LBT failures have been triggered inall UL BWPs with PRACH resources on the serving PCell, the UE maytrigger a radio link failure (RLF) procedure for the PCell.

In another implementation, if consistent UL LBT failures are detected ona BWP on the PSCell (e.g., the LBT_COUNTER reaches thelbt-FailureInstanceMaxCount for the corresponding UL BWP of the PSCell),a PSCell LBT recovery procedure may be initiated. The PSCell LBTrecovery procedure may include a triggering of consistent UL LBTfailures for the corresponding UL BWP and an initiation of an RAprocedure on another BWP (on the PSCell) configured with PRACH resources(e.g., UE-initiated BWP switching to a BWP configured with PRACHoccasion), and for which consistent UL LBT failures has not beentriggered. Additionally, an LBT failure MAC CE (which identifies thefailed Cell and/or BWP) may be reported to the network as part of thePSCell LBT recovery procedure. However, if consistent UL LBT failureshave been triggered on all the (or a BWP_declaration_counter has reacheda configured BWP_declaration_threshold, as described below) BWPs on thePSCell with configured PRACH resources (e.g., PRACH occasion), aprocedure to report SCG failure information may be initiated asdescribed in Citation 3.

FIG. 4 illustrates a flowchart 400 of a method by a UE for an LBTfailure and recovery procedure, according to an example implementationof the present disclosure. As shown in FIG. 4, in action 402, the UE maydetect consistent UL LBT failures on a BWP (BWP_(i)) on a serving cell(e.g., a PSCell). For example, the LBT counter maintained for thisserving PSCell reaches the MaxLBT threshold. In action 404, the UE maytrigger consistent UL LBT failures of the BWP_(i) on the PSCell. Inaction 406, the UE may determine whether the consistent UL LBT failureshave been triggered in all UL BWPs with PRACH resources on the servingPSCell.

In action 408, if the consistent UL LBT failures have not been triggeredin all UL BWPs with the PRACH resources on the serving PSCell, the UEmay switch to a new BWP with PRACH resources on the serving PSCell andfor which consistent UL LBT failures have not been triggered. The UE mayinitiate an RA procedure on the new BWP, and report the LBT failureusing a MAC CE (e.g., an LBT failure MAC CE) in the new BWP during theRA procedure (e.g., on a PUSCH scheduled by an UL grant from RAR). TheUE may also re-initialize any suspended configuration(s) on the new ULBWP. The flowchart 400 may then proceed from action 408 to action 402.

In action 410, if the consistent UL LBT failures have been triggered inall UL BWPs with PRACH resources on the serving PSCell, the UE mayinitiate a procedure to report SCG failure information.

In one implementation, the BWP_declaration_counter may be initially setto zero upon (re-)configuration. The BWP_declaration_counter may bemaintained per cell (or per CG/subset of CG) in order to count thenumber of BWPs that have been triggered with consistent UL LBT failuresfor the corresponding cell. The BWP_declaration_counter (correspondingto a serving cell) may be incremented (by one) each time a BWP (of aserving cell) has been triggered as an invalid BWP (e.g., consistentuplink LBT failures happens on the BWP of a serving cell).

On the other hand, the BWP_declaration_threshold may be configured percell (or per CG/subset of CG). The threshold may be used to define themaximum number of BWPs (of a serving cell) that may be triggered as aninvalid BWP before the UE triggers the RLF procedure as described inCitation 3 or report SCG failure information as described in Citation 3as part of the LBT failure recovery procedure.

In one example, if the value of BWP_declaration_counter (correspondingto the PCell) has reached a BWP_declaration_threshold for the PCell, anRLF may be triggered as described in Citation 3.

In one example, if the value of BWP_declaration_counter (corresponds tothe PSCell) has reached a BWP_declaration_threshold for the PSCell, aprocedure to report SCG failure information may be initiated asdescribed in Citation 3.

In one example, the BWP_declaration_threshold configured for a servingcell may be configured to be equal to the number of BWPs configured withPRACH resources (e.g., PRACH occasion) of the serving cell.

In one implementation, if consistent UL LBT failure(s) is detected on aBWP on an SCell (e.g., the LBT_COUNTER reacheslbt-FailureInstanceMaxCount for the corresponding UL BWP), an SCell LBTrecovery procedure may involve triggering of consistent UL LBT failuresfor the corresponding BWP and reporting an LBT failure MAC CE (whichidentifies the failed Cell and/or BWP) to the network.

FIG. 5 illustrates a flowchart 500 of a method by a UE for an LBTfailure and recovery procedure, according to an example implementationof the present disclosure. In action 502, the UE may detect consistentUL LBT failures on a BWP (BWP_(i)) on a serving cell (e.g., an SCell).For example, the LBT counter maintained for this serving SCell reachesthe MaxLBT threshold. In action 504, the UE may trigger consistent ULLBT failures on the BWP_(i). In action 506, the UE may report an LBTfailure using a MAC CE (e.g., an LBT failure MAC CE).

In one implementation, a UE may report an LBT failure MAC CE whenconsistent UL LBT failures has been detected on a BWP of a SCell or aSpCell. Such a reporting mechanism may include triggering an LBT failureMAC CE(s) (by a BWP or/and serving cell) upon the detection ofconsistent uplink LBT failures on the BWP. Moreover, a triggered LBTfailure MAC CE(s) may be considered as pending until it is beingcancelled. Subsequently, if an UL resource (e.g., a PUSCH resource)becomes available for the transmission of an LBT failure MAC CE, a UEmay generate an LBT failure MAC CE if there is triggered and pending LBTfailure MAC CE(s). The generated LBT failure MAC CE may includeinformation of the BWP and/or serving cell where consistent uplink LBTfailures has been detected. For example, the format of the LBT failureMAC CE may be a bitmap to indicate if a corresponding serving cell hastriggered consistent UL LBT failures. On the other hand, if there is noUL resource for transmitting the LBT failure MAC CE when there istriggered and pending LBT failure MAC CE(s), the UE may trigger an SR.

In one implementation, the triggered LBT failure MAC CE(s) prior to aMAC PDU assembly may be cancelled when a MAC PDU is transmitted, andthis MAC PDU includes an LBT failure MAC CE (plus its subheader) whichcontains LBT information of the BWP(s) and/or serving cell(s) thattriggered the LBT failure MAC CE(s) prior to the MAC PDU assembly.

In one implementation, all triggered LBT failure MAC CE(s) prior to aMAC PDU assembly may be cancelled when a MAC PDU is transmitted, andthis MAC PDU includes an LBT failure MAC CE (plus its subheader) whichcontains LBT information of all the BWP(s) and/or serving cell(s) thattriggered the LBT failure MAC CE (s) prior to the MAC PDU assembly.However, it should be understood that other cancellation mechanisms maynot be precluded.

Handling of (Re)transmission on a UL Resource Scheduled by a Multi-TTIUL Grant

A UE may perform LBT before an UL transmission on a PUSCH resourcescheduled by a multi-TTI UL grant as described above. Subsequently, ifthe UE detects an LBT failure for the UL transmission (e.g., the powerdetected by the UE, which intends to perform the UL transmission, ishigher than a predetermined/configured power threshold) and/or the MAClayer of the UE receives an LBT failure indication from the PHY layer ofthe UE before the start of the PUSCH resource (in the time domain), anda TB for the corresponding PUSCH resource has been generated, the UE maynot transmit the generated TB on the corresponding PUSCH resource. Basedon the agreement from the 3GPP RAN WG2, the generated TB for thecorresponding PUSCH resource may then be transmitted on another PUSCHresource with a different HARQ process ID. For example, the UE may moveor copy the generated TB from a HARQ buffer to another HARQ buffer withthe different HARQ process ID. However, additional conditions may bespecified, considering the processing complexity internally at the UE.

In one implementation, if a UE fails to perform transmission of a TB,namely TB1, on an UL resource (associated with a HARQ process ID)scheduled by a UL grant (e.g., multi-TTI UL grant)) (e.g., ULresource 1) due to detection of an LBT failure, the UE may perform(re)transmission of TB1 on another UL resource with a different HARQprocess ID (e.g., UL resource 2), if one or more or any combination ofthe following conditions are satisfied.

-   -   UL resource 2 and UL resource 1 are both scheduled by the same        multi-TTI UL grant.    -   The grant size of UL resource 2 is equal to or larger than the        size (e.g., TBS) of UL resource 1.    -   UL resource 2 is used for new transmission (e.g., the NDI        corresponding to the HARQ process of UL resource 2 has been        toggled when comparing with the NDI value in the previous        transmission of this HARQ process).    -   Specifically, the NDI value corresponding to the HARQ process of        UL resource 2 may be indicated in the DCI field of (multi-TTI)        UL grant that schedules UL resource 2.    -   UL resource 2 and UL resource 1 are both scheduled by the same        RNTI (e.g., MCS-C-RNTI). UL resource 2 and UL resource 1 are        both scheduled by a same DCI format.    -   UL resource 2 is scheduled to transmit on same BWP and/or        serving cell as UL resource 1.    -   UL resource 2 is scheduled to transmit on different BWP and/or        serving cell as UL resource 1.    -   The grant size of UL resource 2 is less than the size of UL        resource 1.    -   The HARQ buffer corresponds to the HARQ process of UL resource 1        does not contain a TB.    -   The HARQ buffer corresponds to the HARQ process of UL resource 2        does not contain a TB.    -   The TB in the HARQ buffer corresponds to the HARQ process of UL        resource 2 has been transmitted successfully;    -   A TB (other than TB1) that was intended for the transmission on        UL resource 2 has not yet been generated.    -   A TB (other than TB1) that was intended for the transmission on        UL resource 2 does not contain a specific MAC subPDU.    -   Specifically, a specific MAC subPDU may be referred to as a MAC        subPDU with a specific MAC SDU.    -   Furthermore, a specific MAC SDU may consist data from a specific        LCH.    -   Furthermore, a specific LCH may have a specific priority value        as described in Citation 3.    -   Furthermore, a specific LCH may have a specific mapping        restriction(s), e.g., one or more or any combination of        allowedSCS-List, maxPUSCH-Duration, configuredGrantType1Allowed,        and allowedServingCells as described in Citation 3. Furthermore,        a specific LCH may be a DCCH or a CCCH.    -   Specifically, a specific MAC subPDU may be referred to as a MAC        subPDU with a specific MAC CE.    -   Furthermore, a specific MAC CE may be (but is not limited to be)        a Configured Grant Confirmation MAC CE, SCell BFR MAC CE, MAC CE        for BSR except for BSR included for padding, PHR MAC CE, MAC CE        for Recommended bit rate query, MAC CE for BSR included for        padding, etc.    -   UL resource 2 is the first (or the next) resource that occurs        after UL resource 1.    -   UL resource 2 and UL resource 1 has the same redundancy version.    -   UL resource 2 is a first PUSCH resource for which LBT is        successful after UL resource 1.    -   UL resource 2 is not used for multiplexing of aperiodic CSI        reports.    -   If UL resource 2 is the first (or the next) configured uplink        grant resource that occur after a specific interval upon LBT        failure corresponding to the UL resource 1.    -   UL resource 1 is used for new transmission (e.g., the NDI        corresponding to the HARQ process of UL resource 1 has been        toggled when comparing with the NDI value in the previous        transmission of this HARQ process). Specifically, the NDI value        corresponding to the HARQ process of UL resource 1 may be        indicated in the DCI field of (multi-TTI) UL grant that        schedules UL resource 1.    -   UL resource 2 is used for retransmission (e.g., the NDI        corresponding to the HARQ process of UL resource 2 has not been        toggled when comparing with the NDI value in the previous        transmission of this HARQ process).    -   Specifically, the NDI value corresponding to the HARQ process of        UL resource 2 may be indicated in the DCI field of (multi-TTI)        UL grant that schedules UL resource 2.    -   An UL grant for retransmission of the TB1 is not received by the        UE before UL resource 2 and after UL resource 1.    -   The TB to be transmitted on UL resource 1 contains a specific        MAC subPDU.    -   Specifically, a specific MAC subPDU may be referred to as a MAC        subPDU with a specific MAC SDU.    -   Furthermore, a specific MAC SDU may consist data from a specific        LCH.    -   Furthermore, a specific LCH may have a specific priority value        as described in Citation 3.    -   Furthermore, a specific LCH may have a priority value which is        equal or higher/lower than a specific threshold which may be        preconfigured by the gNB.    -   Furthermore, a specific LCH may have a specific mapping        restriction(s), e.g., one or more or any combination of        allowedSCS-List, maxPUSCH-Duration, configuredGrantType1Allowed,        and allowedServingCells as described in Citation 3.    -   Furthermore, a specific LCH may be a DCCH or a CCCH.    -   Specifically, a specific MAC subPDU may be referred to as a MAC        subPDU with a specific MAC CE.    -   Furthermore, a specific MAC CE may be (but is not limited to be)        a Configured Grant Confirmation MAC CE, SCell BFR MAC CE, MAC CE        for BSR except for BSR included for padding, PHR MAC CE, MAC CE        for Recommended bit rate query, MAC CE for BSR included for        padding, etc.    -   (the starting symbol/the ending symbol of) UL resource 2 occurs        at least a specific period after (the starting symbol/the ending        symbol of) UL resource 1.    -   More specifically, the specific period may be configured by the        network or preconfigured by the UE.    -   More specifically, the specific period may consider the timeline        requirements which essentially require a minimum duration        between DCI scheduling a PUSCH and the PUSCH transmission. This        value may be derived by the formula provided in TS 38.214 as        described in Citation 4, which considers the UE processing        capability (e.g., UE processing capability 1 or UE processing        capability 2).    -   The UE is configured, by the network, a specific information        element (IE), which indicates that the UE is allowed to perform        the (re)transmission of the TB1 on another UL resource        associated with different HARQ process ID (that is also        scheduled by the same multi-TTI UL grant that schedules UL        resource 1).    -   More specifically, the Serving Cell group/serving cell/UL BWP        associated with the PUSCHs granted by the multi-TTI UL grant may        be configured, by the network, a specific information element        (IE), which indicates whether the UE is allowed to perform the        (re)transmission of the TB1 on another UL resource associated        with a different HARQ process ID (that is also scheduled by the        same multi-TTI UL grant that schedules UL resource 1);    -   More specifically, the UE may be indicated, by the network, via        the Time domain resource assignment field within the DCI of the        multi-TTI UL grant. For example, the network indicates a        specific SLIV value which associates with a specific row of the        PUSCH TDRA table, wherein the specific row was pre-defined with        whether the corresponding PUSCH transmission allow        (re)transmission TB via different HARQ process.

Otherwise, the UE may not perform (re)transmission of TB1 on another ULresource with a different HARQ process ID. Furthermore, if the UEdecides to perform (re)transmission of TB1 on another UL resource with adifferent HARQ process ID, the UE may flush the HARQ buffer of the HARQprocess corresponding the TB1.

In one implementation, if a UE fails to perform transmission a TB (e.g,TB1) on a UL resource (e.g., UL resource 1) scheduled by a multi-TTI ULgrant (due to LBT failure), the UE may perform (re)transmission of TB1on another UL resource (e.g., UL resource 2) with a different HARQprocess ID, if UL resource 1 and UL resource 2 have the same grant sizeand are both scheduled by the same multi-TTI UL grant.

FIG. 6 illustrates a diagram for handling (re)transmission on a ULresource scheduled by a multi-TTI UL grant, according to an exampleimplementation of the present disclosure. At time T₆₀₁, the UE mayreceive a dynamic grant (e.g., a multi-TTI UL grant) for scheduling oneor more UL resources. In one implementation, the dynamic grant isreceived by the UE in DCI. In the present implementation, the dynamicgrant may schedule a first UL resource (e.g., a PUSCH resource) having aHARQ ID (e.g., HARQ ID=2) and a second UL resource (e.g., another PUSCHresource) having another HARQ ID (e.g., HARQ ID=1). In the presentimplementation, the second UL resource and the first UL resource may beconsecutive resources in the time domain. As illustrated in FIG. 6, thefirst UL resource may be immediately after the second UL resource in thetime domain.

At time T₆₀₂, the UE may generate a second MAC PDU for transmission onthe second UL resource as scheduled by the dynamic grant. The second MACPDU is stored in a HARQ buffer after being generated, and the HARQbuffer is associated with a HARQ process of the second UL resource. TheUE may also start an LBT procedure to determine if the second ULresource is available for transmitting the second MAC PDU.

At time T₆₀₃, the UE may determine that the LBT procedure for the secondUL resource has failed. For example, the UE may receive an LBT failureindication indicating that the second UL resource cannot be used fortransmitting the second MAC PDU. The UE may subsequently start anotherLBT procedure to determine if the first UL resource is available fortransmission.

At time T₆₀₄, the UE may determine whether the first UL resource issuitable for transmitting the second MAC PDU. The first UL resource issuitable for transmitting the second MAC PDU if at least one of theabove-mentioned conditions is satisfied.

Based on whether the first UL resource is suitable for transmitting thesecond MAC PDU, the UE may determine whether to obtain a first MAC PDUfor transmission using the first UL resource or to transmit the alreadygenerated second MAC PDU before obtaining the first MAC PDU. Forexample, if the first UL resource is suitable for transmitting thesecond MAC PDU, the UE may decide to transmit the already generatedsecond MAC PDU (and has been stored in the HARQ buffer) before obtainingthe first MAC PDU. If the first UL resource is not suitable fortransmitting the second MAC PDU, the UE may obtain a first MAC PDU fortransmission using the first UL resource. Moreover, obtaining the firstMAC PDU may include generating the first MAC PDU or retrieving the firstMAC PDU. In one example, after determining the first UL resource is notsuitable for transmitting the second MAC PDU, the UE may generate a newMAC PDU (e.g., the first MAC PDU) if the first UL resource is indicatedfor a new transmission (e.g., the NDI corresponding to the HARQ processof the first UL resource has been toggled when comparing with the NDIvalue in the previous transmission of this HARQ process). In anotherexample, after determining the first UL resource is not suitable fortransmitting the second MAC PDU, the UE may retrieve a MAC PDU (e.g.,the first MAC PDU) that is already generated and stored in the HARQbuffer associated with the HARQ process of the first UL resource if thefirst UL resource is indicated for a retransmission (e.g., the NDIcorresponding to the HARQ process of the first UL resource has not beentoggled when comparing with the NDI value in the previous transmissionof this HARQ process).

At time T₆₀₅, the UE may determine that the LBT for the first ULresource has succeeded. For example, the UE does not receive an LBTfailure indication. Thus, the first UL resource is available, and can beused for transmission.

At time T₆₀₆, the UE may transmit the second MAC PDU using the first ULresource when the first UL resource is suitable for transmitting thesecond MAC PDU. For example, the UE may obtain the second MAC PDU fromthe HARQ buffer associated with the HARQ process of the second ULresource, and transmit the second MAC PDU using the first UL resource.Alternatively, when it is determined that the first UL resource is notsuitable for transmitting the second MAC PDU, the UE may transmit thefirst MAC PDU using the first UL resource. In the present example, thefirst UL resource may be considered suitable for transmitting the secondMAC PDU if the second UL resource and the first UL resource are eachintended for a new transmission, and the size (e.g., TBS) of the firstUL resource is equal to the size (e.g., TBS) of the second UL resource.In contrast, the first UL resource may be considered not suitable fortransmitting the second MAC PDU if the second UL resource and the firstUL resource are not both intended for a new transmission (e.g., thesecond UL resource is intended for new transmission and first ULresource is intended for retransmission or vice versa) or if the size(e.g., TBS) of the first UL resource is not equal to the size (e.g.,TBS) of the second UL resource.

FIG. 7 illustrates a flowchart 700 of a method by a UE for handling(re)transmission on a UL resource scheduled by a multi-TTI UL grant,according to an example implementation of the present disclosure.

In action 702, the UE may receive a dynamic grant (e.g., a multi-TTI ULgrant) for scheduling one or more UL resources. In one implementation,the dynamic grant is received by the UE in a DCI. With reference to FIG.6, the dynamic grant may schedule a first UL resource (e.g., a PUSCHresource) having a HARQ ID (e.g., HARQ ID=2) and a second UL resource(e.g., another PUSCH resource) having another HARQ ID (e.g., HARQ ID=1).The second UL resource and the first UL resource may be consecutiveresources in the time domain, where the first UL resource may beimmediately after the second UL resource. In the present implementation,at least one of the second UL resource and the first UL resource may beintended for a new transmission. For example, each of the second ULresource and the first UL resource is intended for a new transmission.In another example, the second MAC PDU is for a new transmission and thefirst MAC PDU is for retransmission, or vice versa. In oneimplementation, the size of the first UL resource may be equal to orgreater than the size of the second UL resource.

In action 704, the UE may generate a second MAC PDU for transmission onthe second UL resource as scheduled by the dynamic grant. The second MACPDU is stored in a HARQ buffer after being generated, and the HARQbuffer is associated with a HARQ process of the second UL resource.

In action 706, the UE may start an LBT procedure to determine whetherthe second UL resource is available for transmitting the second MAC PDU.

In action 708, the UE may determine that the LBT procedure for thesecond UL resource has failed. For example, the UE may receive an LBTfailure indication (e.g., the MAC layer of the UE may receive an LBTfailure indication from the PHY layer of the UE) indicating that thesecond UL resource cannot be used for transmitting the second MAC PDU.Consequently, the UE may start an LBT procedure to see if the first ULresource is available for transmission.

In action 710, the UE may start another LBT procedure to determinewhether the first UL resource is available for transmission.

In action 712, the UE may determine whether the first UL resource issuitable for transmitting the second MAC PDU. For example, based onwhether the first UL resource is suitable for transmitting the secondMAC PDU, the UE may determine whether to obtain a first MAC PDU fortransmission using the first UL resource, or to transmit the alreadygenerated second MAC PDU before obtaining the first MAC PDU.

In one implementation, the first UL resource is suitable fortransmitting the second MAC PDU if at least one of the followingconditions is satisfied:

-   -   the second MAC PDU is generated for transmission using a second        UL resource scheduled by the dynamic grant;    -   the second UL resource is indicated for another new        transmission;    -   the second UL resource is before the first UL resource in a time        domain;    -   the size of the first UL resource is equal to or greater than        the size of the second UL resource;    -   the second MAC PDU is not transmitted successfully on the second        UL resource due to a UL LBT failure; and    -   the second UL resource associated with the second HARQ ID is        different from the first HARQ ID associated with the first UL        resource.

If the UE determines that the first UL resource is suitable fortransmitting the second MAC PDU, the flowchart 700 proceeds from action712 to action 714. In action 714, the UE may determine that the LBT forthe first UL resource has succeeded. For example, the UE does notreceive an LBT failure indication. Thus, the first UL resource isavailable, and can be used for transmission of the second MAC PDU. Inaction 716, the UE may transmit the second MAC PDU using the first ULresource. For example, the UE may obtain the second MAC PDU from theHARQ buffer, and transmit the second MAC PDU using the first ULresource.

If the UE determines that the first UL resource is not suitable fortransmitting the second MAC PDU, the flowchart 700 proceeds from action712 to action 718. In action 718, the UE may obtain a first MAC PDU fortransmission on the first UL resource as scheduled by the dynamic grant.Moreover, obtaining the first MAC PDU may include generating a new MACPDU or retrieving a stored (e.g., previously generated) MAC PDU from aHARQ buffer. In one example, after determining the first UL resource isnot suitable for transmitting the second MAC PDU, the UE may generatethe first MAC PDU (e.g., a new MAC PDU) if the first UL resource isindicated for a new transmission (e.g., the NDI corresponding to theHARQ process of the first UL resource has been toggled when comparingwith the NDI value in the previous transmission of this HARQ process).In another example, after determining the first UL resource is notsuitable for transmitting the second MAC PDU, the UE may retrieve thefirst MAC PDU that is already generated and stored in the HARQ bufferassociated with the HARQ process of the first UL resource if the firstUL resource is indicated for retransmission (e.g., the NDI correspondingto the HARQ process of the first UL resource has not been toggled whencomparing with the NDI value in the previous transmission of this HARQprocess). In action 720, the UE may determine that the LBT for the firstUL resource has succeeded. For example, the UE does not receive an LBTfailure indication. Thus, the first UL resource is available, and can beused for transmission of the first MAC PDU. In action 722, the UE maytransmit the first MAC PDU using the first UL resource. In the presentexample, the UE may determine that the first UL resource is suitable fortransmitting the second MAC PDU because all the conditions:

-   -   the second MAC PDU is generated for transmission using a second        UL resource scheduled by the dynamic grant;    -   the second UL resource is indicated for another new        transmission;    -   the second UL resource is before the first UL resource in a time        domain;    -   the size of the first UL resource is equal to the size of the        second UL resource;    -   the second MAC PDU is not transmitted successfully on the second        UL resource due to a UL LBT failure; and    -   the second UL resource associated with the second HARQ ID is        different from the first HARQ ID associated with the first UL        resource,        are satisfied.

In one implementation, if a UE fails to perform transmission a TB (e.g.,TB1) on a UL resource (e.g., UL resource 1) scheduled by a multi-TTI ULgrant (due to LBT failure), the UE may perform (re)transmission of TB1on another UL resource (e.g., UL resource 2) with a different HARQprocess ID, if TB1 contains a specific MAC subPDU with at least one MACSDU consisting data from a DCCH. The reason is that the DCCH may bemapped to signaling radio bearers (e.g., SRB1 and SRB2). Hence, the datafrom the DCCH may be more important and requires special handling.

In one implementation, if a UE fails to perform transmission a TB (e.g.,TB1) on a UL resource (e.g., UL resource 1) scheduled by a multi-TTI ULgrant (due to LBT failure), the UE may perform (re)transmission of TB1on another UL resource (e.g., UL resource 2) with a different HARQprocess ID, if UL resource 1 and UL resource 2 are both scheduled by thesame multi-TTI UL grant and UL resource 2 is used for a new transmission(e.g., the NDI corresponding to the HARQ process of UL resource 2 hasbeen toggled when comparing with the NDI value in the previoustransmission of this HARQ process). Moreover, another TB (different fromTB1) for UL resource 2 has not yet been generated. In thisimplementation, the UE may also flush the HARQ buffer corresponding tothe HARQ process of UL resource 1.

In one implementation, if a UE fails to perform transmission a TB (e.g.,TB1) on a UL resource (e.g., UL resource 1) scheduled by a multi-TTI ULgrant (due to LBT failure), the UE may perform (re)transmission of TB1on another UL resource (e.g., UL resource 2) with a different HARQprocess ID. However, if the grant size of the UL resource 2 does notmatch with size of the TB1, the UE may indicate to the multiplexing andassembly entity to include MAC subPDU(s) carrying MAC SDU from TB1 inthe subsequent UL transmission (s) (e.g., transmission on UL resource2), and obtain the MAC PDU to transmit on UL resource 2 from themultiplexing and assembly entity.

In one implementation, if a UE fails to perform transmission a TB (e.g.,TB1) on a UL resource (e.g., UL resource 1) scheduled by a multi-TTI ULgrant (due to LBT failure), the UE may perform (re)transmission of TB1on another UL resource (e.g., UL resource 2) with a different HARQprocess ID, if UL resource 1 and UL resource 2 are both scheduled by thesame multi-TTI UL grant and UL resource 1 and UL resource 2 are eachused for a new transmission (e.g., the NDI corresponding to the HARQprocesses of UL resource 1 and UL resource 2 have been toggled whencomparing with the NDI value in the previous transmission of these HARQprocesses). Moreover, the UE generates TB2 for the HARQ processcorresponding to UL resource 1 and stores TB2 in the HARQ buffercorresponding to UL resource 1.

Avoid Transmission Gaps within PUSCHs Scheduled by a Multi-TTI UL GrantDue to skipUplinkTxDynamic

In NR, a PUSCH scheduled by a dynamic grant can be skipped if the MACentity of a UE is configured with skipUplinkTxDynamic and the conditionslisted below are satisfied as described in Citation 5:

-   -   The grant indicated to the HARQ entity was addressed to a        C-RNTI.    -   There is no aperiodic CSI requested for this PUSCH transmission        as specified in TS 38.212.    -   the MAC PDU includes zero MAC SDUs.    -   the MAC PDU includes only the periodic BSR and there is no data        available for any LCH, or the MAC PDU includes only the padding        BSR.

Hence, if skipUplinkTxDynamic is configured with value true for a MACentity, a PUSCH scheduled by a multi-TTI UL grant may be skipped by a UEif the above-mentioned conditions are satisfied. However, in someimplementations, a transmission gap could potentially be introducedbetween PUSCH resources scheduled by a multi-TTI UL grant.

FIG. 8 illustrates a multi-TTI UL grant that schedules multiple PUSCHresources, in accordance with an example implementation of the presentdisclosure. At time T₈₀₁, the UE may receive a dynamic grant (e.g., amulti-TTI UL grant) for scheduling one or more UL resources. In oneimplementation, the dynamic grant is received by the UE in DCI. In thepresent implementation, the dynamic grant may schedule a first ULresource (e.g., PUSCH 1), a second UL resource (e.g., PUSCH 2), and athird UL resource (e.g., PUSCH 3). In the present implementation, PUSCH1, PUSCH 2, and PUSCH 3 are consecutive resources in the time domain. Attime T₈₀₂, the UE may determine that the LBT procedure has succeeded.For example, the UE does not receive an LBT failure indication. Thus,PUSCH 1 and PUSCH 2 are available, and can be used for transmission.

If the UE decided to skip the transmission of PUSCH 2 (e.g., the UE doesnot generate a TB for transmission on PUSCH 2), it would be required toperform LBT for subsequent PUSCH(s) scheduled by the same multi-TTI ULgrant (e.g., PUSCH 3) even though LBT has already been successful on theearlier scheduled PUSCH(s) (e.g., PUSCH 1). In the presentimplementation, the UE may ignore the configuration ofskipUplinkTxDynamic and generate a MAC PDU (e.g., a filler PDU) fortransmission PUSCH 2, so that the UE does not have to perform LBT beforetransmission using PUSCH 3. In the present implementation, the UE mayconditionally disable skipping of PUSCH scheduled by a multi-TTI ULgrant even when skipUplinkTxDynamic is configured with value true. Assuch, the UE may avoid the transmission gap(s) within PUSCHs scheduledby the multi-TTI UL grant due to the skipUplinkTxDynamic.

In another implementation, the UE may transmit a PUSCH, namely PUSCH 1,scheduled by a dynamic grant (e.g., dynamic grant 1) addressed toC-RNTI. Despite all conditions in category A has been satisfied, the UEmay still transmit on PUSCH 1 (e.g., The MAC entity may still generate aMAC PDU for the HARQ process corresponding to PUSCH 1) if one or more orany combination of the conditions in category B are satisfied.Alternatively, the UE may ignore the configuration ofskipUplinkTxDynamic if one or more or any combination of the conditionsin category B are satisfied. Alternatively, the UE may consider theconfiguration of skipUplinkTxDynamic as false if one or more or anycombination of the conditions in category B are satisfied.

Conditions in Category A:

-   -   skipUplinkTxDynamic is configured for the UE (e.g., configured        for the MAC entity of the UE).    -   There is no aperiodic CSI requested for PUSCH 1 transmission as        specified in TS 38.212 as described in Citation 6.    -   the MAC PDU includes zero MAC SDUs.    -   the MAC PDU includes only the periodic BSR and there is no data        available for any LCH, or the MAC PDU includes only the padding        BSR.

Conditions in Category B:

-   -   The UL resource(s) is scheduled on an un-licensed spectrum.    -   Dynamic grant 1 is a multi-TTI UL grant.    -   More specifically, dynamic grant 1 may allocate more than one        PUSCH resources, whereas PUSCH 1 is one of the multiple PUSCH        resources allocated by dynamic grant 1.    -   More specifically, PUSCH 1 is not the last PUSCH resources        allocated by dynamic grant 1.    -   Dynamic grant 1 is a multi-TTI UL grant and PUSCH 1 is not the        earliest or latest PUSCH (in the time domain) out of all the        PUSCHs scheduled by dynamic grant 1.    -   More specifically, dynamic grant 1 may allocate multiple PUSCH        resources that are contiguous in the time domain.    -   Dynamic grant 1 is a multi-TTI UL grant and PUSCH 1 is the PUSCH        for multiplexing aperiodic CSI report or is the PUSCH before the        PUSCH for multiplexing aperiodic CSI report.    -   More specifically, dynamic grant 1 may allocate multiple PUSCH        resources that are contiguous in the time domain.    -   Dynamic grant 1 is a multi-TTI UL grant and PUSCH 1 is a PUSCH        overlapping with a PUCCH for transmission of HARQ-ACK or CSI        report.    -   More specifically, dynamic grant 1 may allocate multiple PUSCH        resources that are contiguous in the time domain.    -   The time duration of PUSCH 1 is longer than a specific value.    -   More specifically, the specific value may be configured by the        network or preconfigured by the UE.    -   More specifically, the specific value may be the maximum time        gap between UL transmissions that belong to the same UL burst,        e.g., 16 microseconds as described in Citation 1.    -   Dynamic grant 1 is a multi-TTI UL grant and the transmission has        been successfully performed for PUSCH(s) that are scheduled by        dynamic grant 1 and occur earlier than PUSCH 1.    -   In one case, if the PUSCH(s) that are also scheduled by dynamic        grant 1 and occur earlier than PUSCH 1 in the time domain was        successfully transmitted, the UE may not need to perform LBT        before PUSCH 1 transmission because PUSCH 1 may be still within        the COT obtained by the UE. In this case, the UE may still        perform transmission in PUSCH 1 if all the conditions in        category A are satisfied. As such, a transmission gap may be        avoided. In one case, if the PUSCH(s) that are also scheduled by        dynamic grant 1 and occur earlier than PUSCH 1 in the time        domain was not successfully transmitted, the UE may need to        perform LBT before PUSCH 1 transmission. In this case, the UE        may skip the transmission PUSCH 1 if all the conditions are        satisfied in category A.

In one aspect of the present implementation, what could be transmittedon PUSCH 1 may be (but is not limited to) one or multiple of thefollowing contents:

-   -   A MAC subPDU including a short BSR MAC CE (and its corresponding        MAC subheader).    -   A MAC subPDU including a BFR MAC CE (and its corresponding MAC        subheader).    -   A MAC subPDU including padding (and its corresponding MAC        subheader).    -   A MAC subPDU with a MAC subheader only.

In one implementation, the network may indicate (via RRC signaling, DCI,MAC CE, etc.) whether a UE should perform transmission on all thereceived PUSCH resources scheduled by a dynamic grant (and is amulti-TTI UL grant). Such a configuration may be configured perBWP/Cell/subset of CG. The UE may not skip the transmission on anyreceived PUSCH resource scheduled by a dynamic grant (and is a multi-TTIUL grant) on the indicated BWP/Cell/subset of CG even if all theconditions in category A has been satisfied.

In one implementation, the network may indicate (via RRC signaling, DCI,MAC CE, etc.) whether a UE should perform transmission on all thereceived PUSCH resources that corresponds to a configured UL grantconfiguration. Such a configuration may be configured perBWP/Cell/subset of CG. The UE may not skip the transmission on anyreceived PUSCH resource that corresponds to a configured UL grantconfiguration on indicated BWP/Cell/subset of CG.

In one implementation, the network may not configure skipUplinkTxDynamicfor a UE or may need to configure skipUplinkTxDynamic with value falsefor a UE, if the UE is configured with multi-TTI UL grant.

Specifically, the UE may be considered as being configured withmulti-TTI UL grant if it is configured, by the network (via RRCsignaling), a TDRA list (e.g., pusch-TimeDomainAllocationList-r16 IE)with at least one row that includes the time-domain relationship betweenone PDCCH and multiple PUSCH resource allocations (e.g., a row thatincludes more than one startSymbolAndLength values).

In one implementation, the network may not configure skipUplinkTxDynamicfor a UE or may need to configure skipUplinkTxDynamic with value falsefor a UE, if the UE is configured with NR-U functionality.

In one implementation, even if a UE is configured skipUplinkTxDynamicand with a value of true, the UE may not generate a MAC PDU uponreception dynamic grant if conditions in category A are satisfied andthe PUSCH scheduled by the dynamic grant is in a licensed serving cell.Specifically, the UE may be considered as being configured with NR-Ufunctionality by the presence of specific NR-U related configurations.For example, by the presence of NRU-UplinkLbtFailureConfig-r16 IE,RMTC-Config-r16 IE, additionalMonitoringOccasionOfPO-r16 IE, etc. Morespecifically, the UE may be considered as being configured with NR-Ufunctionality if it has indicated the network that it is capable ofsupporting NR-U functionality. Such a capability information may beconveyed via UE capability RRC signaling (e.g., UE-NR-Capability IE).

Suspension of UL Transmission Upon BWP Switching Due to Consistent ULLBT Failures on a SpCell

Upon consistent UL LBT failures on an UL BWP of a SpCell (e.g.,LBT_COUNTER reaches lbt-FailureInstanceMaxCount for the corresponding ULBWP of the SpCell), a UE may trigger consistent UL LBT failure for thecorresponding UL BWP. Subsequently, if not all the UL BWP(s) configuredwith PRACH occasions (e.g., PRACH resource) of the SpCell has beentriggered with consistent UL LBT failure, the UE may switch to a new ULBWP configured with PRACH occasion (e.g., PRACH resource), and for whichconsistent UL LBT failure has not been triggered (as shown in FIGS. 3and 4). Thereafter, the UE may initiate an RA procedure on the new ULBWP. In this case, it may not be desirable for the UE to directlyperform a specific UL transmission on the new UL BWP. Here, a specificUL transmission may be referred to as (but is not limited to be) type 1configured grant transmission on PUSCH, periodic CSI reporting on PUCCH,semi-persistent CSI reporting on PUCCH, periodic SRS transmission onPUCCH. One reason is that the network is not aware of the UE-initiatedUL BWP switching due to consistent UL LBT failures on the SpCell.Another reason is that the channel condition of the new UL BWP may beuncertain before the RA procedure on the new UL BWP is successfullycompleted (e.g., before the SpCell LBT recovery procedure issuccessfully completed). Allowing direct UL transmission attempt on thenew UL BWP may not be a proper UE behavior, at a risk of UL LBT failureand unsuccessful UL transmission. Therefore, certain mechanisms may beintroduced to conditionally allow the resumption of UL transmission uponactivation of an inactive BWP (due to BWP switching).

In one implementation, consistent UL LBT failures may occur on an old ULBWP of a SpCell (e.g., LBT_COUNTER reaches lbt-FailureInstanceMaxCountfor the corresponding UL BWP of the SpCell) of a UE, which results inUE-initiated BWP switch to a new UL BWP configured with PRACH occasion(e.g., PRACH resource) and for which consistent UL LBT failure has notbeen triggered. Subsequently, the UE may perform update process(es) uponswitching to the new UL BWP. The update process(es) may be one or moreor any combination of the following:

-   -   Postpone specific UL transmission(s) on the new UL BWP.    -   More specifically, a specific UL transmission may be an SRS        transmission, transmission of aperiodic/semi-static CSI report        or other UCIs (e.g., SR or HARQ feedback) on PUCCH resource,        transmission on PUSCH resources that corresponds to a configured        grant Type 1 configuration, etc.    -   More specifically, the UE may postpone the specific UL        transmission(s) on the new UL BWP until the RA procedure        (triggered due to consistent UL LBT failures) on the new UL BWP        is successfully completed.    -   Postpone (re-)initialization of any suspended configuration(s)        on the new UL BWP.    -   In one implementation, a suspended configuration may be a        configuration of configured grant Type 1, a configuration of        periodic SRS, a configuration of semi-static SRS, a        configuration of periodic CSI reporting (on PUCCH resource), a        configuration of semi-static CSI reporting (on PUCCH resource).        Those configurations may be configured, by the network, via RRC        signaling.

A further update process(es) may be one or more or any combination ofthe following:

-   -   The UE may postpone the specific UL transmission(s) on the new        UL BWP until one or more or any combination of the conditions in        category C has been satisfied.    -   More specifically, a specific UL transmission may be an SRS        transmission, transmission of aperiodic/semi-static CSI report        or other UCIs (e.g., SR or HARQ feedback) on PUCCH resource,        transmission on PUSCH resources that corresponds to a configured        grant Type 1 configuration, etc.    -   (re-)initialization of any suspended configuration(s) on the new        UL BWP when one or more or any combination of the conditions in        category C has been satisfied.    -   In one implementation, a suspended configuration may be a        configuration of configured grant Type 1, a configuration of        periodic SRS, a configuration of semi-static SRS, a        configuration of periodic CSI reporting (on PUCCH resource), a        configuration of semi-static CSI reporting (on PUCCH resource).        Those configurations may be configured, by the network, via RRC        signaling.

Conditions in Category C:

-   -   Upon successful completion of an RA procedure (that is initiated        as part of the SpCell LBT recovery procedure) on the new UL BWP.    -   In one example, consistent UL LBT failures may occur on an old        UL BWP of a SpCell (e.g., LBT_COUNTER reaches        lbt-FailureInstanceMaxCount for the corresponding UL BWP of the        SpCell) of a UE, which results in UE-initiated BWP switch to a        new UL BWP configured with PRACH occasion (e.g., PRACH resource)        and for which consistent UL LBT failures has not been triggered.        Subsequently, the UE may (re-)initialize a suspended        configuration (e.g., configured grant Type 1, periodic SRS        configuration, periodic CSI reporting, etc.) on the new UL BWP        after the RA procedure has been successfully completed on the        new UL BWP.    -   Upon successful completion of an LBT recovery procedure of the        SpCell.    -   In one example, consistent UL LBT failures may occur on an old        UL BWP of a SpCell (e.g., LBT_COUNTER reaches        lbt-FailureInstanceMaxCount for the corresponding UL BWP of the        SpCell) of a UE, then the UE may initiate an LBT recovery        procedure for the SpCell.    -   Upon transmission of an LBT failure MAC CE (as part of the        SpCell LBT recovery procedure).    -   Specifically, the LBT failure MAC CE may be transmitted after        the UE switches to the new UL BWP.    -   Specifically, the LBT failure MAC CE may identify the BWP(s)        and/or cells where consistent UL LBT failure(s) has been        detected.    -   Specifically, the LBT failure MAC CE may be transmitted via an        UL resource allocated on a different serving from the serving        cell where the SpCell LBT recovery procedure has been initiated        or be transmitted via any available UL resource without        restriction.    -   Specifically, the LBT failure MAC CE may include the LBT        information (e.g., BWP ID and/or cell ID) of all (or part of)        the BWP(s) (or serving cell(s)) that triggered LBT failure MAC        CE(s) prior to the MAC PDU assembly carrying the LBT failure MAC        CE (plus its subheader).    -   If the UE instructs the Multiplexing and Assembly procedure to        generate the LBT failure MAC CE, the UE may perform the        Multiplexing and assembly procedure (including Logical Channel        prioritization procedure) as described in Citation 5. During the        multiplexing and assembly procedure, the UE may multiplex the        generated MAC CE(s) and/or MAC SDU(s) in a MAC PDU. Then the UE        may transmit the MAC PDU (e.g., via a UL-SCH resource). More        specifically, MAC PDU assembly can happen at any point in time        between uplink grant reception and actual transmission of the        corresponding MAC PDU.    -   In one example, consistent UL LBT failures may occur on an old        UL BWP of a SpCell (e.g., LBT_COUNTER reaches        lbt-FailureInstanceMaxCount for the corresponding UL BWP of the        SpCell) of a UE, which results in UE-initiated BWP switch to a        new UL BWP configured with PRACH occasion (e.g., PRACH resource)        and for which consistent UL LBT failures has not been triggered.        Subsequently, the UE may (re-)initialize a suspended        configuration (e.g., configured grant Type 1, periodic SRS        configuration, periodic CSI reporting, etc.) on the new UL BWP        after an LBT failure MAC CE has been successfully transmitted.        (Moreover, this LBT failure MAC CE includes LBT information        (e.g., BWP ID and/or cell ID) of all the serving cell(s) that        triggered LBT failure MAC CE(s) prior to the MAC PDU assembly        carrying the LBT failure MAC CE).    -   Upon determination of a positive response from the network        corresponding to the transmitted LBT failure MAC CE.    -   Specifically, a positive response may be explicitly indicated        from the network or implicitly determined by the UE itself. If a        positive response is determined/received by the UE, it implies        the network has successfully received the LBT failure MAC CE,        which was transmitted by the UE as part of the SpCell LBT        recovery procedure.    -   In one implementation, a positive response may be an explicit DL        HARQ feedback from the network (e.g., an explicit DL HARQ-ACK),        which indicates the HARQ process of an UL transmission that        includes an LBT failure MAC CE has been successfully received.    -   In one implementation, a positive response may be implicitly        determined by a UE upon reception of an (dynamic) UL grant for        new transmission (e.g., with toggled NDI), whereas the (dynamic)        UL grant corresponds to the same HARQ process ID as the UL        resource where an LBT failure MAC CE was transmitted.    -   In one implementation, a positive response may be implicitly        determined by a UE upon a specific timer expires. For example,        the specific timer may be (re-)started upon the transmission of        the LBT failure MAC CE.    -   In one implementation, if an LBT failure MAC CE was transmitted        on a configured UL grant resource (e.g., a PUSCH resource that        corresponds to a configured grant configuration), the positive        response may be implicitly determined by the UE that transmitted        the LBT failure MAC CE. For example, upon expiration of a        configuredGrantTimer as described in Citation 5 for the HARQ        process of a configured UL grant resource (e.g., a PUSCH        resource that corresponds to a configured grant configuration)        where the LBT failure MAC CE was transmitted.    -   Specifically, the configured grant configuration may be (but is        not limited to be) a configured grant Type 1/configured grant        Type 2 configuration.    -   In one implementation, if an LBT failure MAC CE was transmitted        on a Msg 3 (e.g., transmitted on a PUSCH resource scheduled by        an RAR, which corresponds to an RA procedure initiated as part        of the SpCell LBT failure recovery procedure), the positive        response may be an explicit HARQ-ACK from the network, e.g., a        PDCCH address to C-RNTI (that contains an UL grant for new        transmission) indicated by the network while the        ra-ContentionResolutionTimer as described in Citation 5 is        running.    -   In one example, consistent UL LBT failures may occur on an old        UL BWP of a SpCell (e.g., LBT_COUNTER reaches        lbt-FailureInstanceMaxCount for the corresponding UL BWP of the        SpCell) of a UE, which results in UE-initiated BWP switch to a        new UL BWP configured with PRACH occasion (e.g., PRACH resource)        and for which consistent UL LBT failures has not been triggered.    -   Subsequently, the UE may transmit an LBT failure MAC CE (which        includes LBT information (e.g., BWP ID and/or cell ID) of all        the serving cell(s) that triggered LBT failure MAC CE(s) prior        to the MAC PDU assembly carrying the LBT failure MAC CE).        Subsequently, the UE may (re-)initialize a suspended        configuration (e.g., configured grant Type 1, periodic SRS        configuration, periodic CSI reporting, etc.) on the new UL BWP        after determine/receiving a positive response (from the network)        corresponding to a transmitted LBT failure MAC CE.    -   In one case, if the MAC CE is transmitted on an UL resource with        HARQ process 1, the network may signal a positive response via a        PDCCH (addressed to C-RNTI) indicating an UL grant for a new        transmission (with toggled NDI) for HARQ process 1.    -   In one case, if the MAC CE is transmitted on an UL resource with        HARQ process 1, and for which corresponds to a configured UL        grant configuration, the network may signal a positive response        via an explicit DL HARQ feedback (e.g., DFI) with HARQ process        1.    -   In one case, if the MAC CE is transmitted on an UL resource with        HARQ process 1, and for which corresponds to a configured UL        grant configuration, the UE may determine a positive response        upon expiration of the configuredGrantTimer as described in        Citation 5 which corresponds to HARQ process 1. In this case,        the configuredGrantTimer is start upon transmission of the MAC        CE on the UL resource.    -   In one case, if the LBT failure MAC CE is transmitted on a Msg 3        (e.g., transmitted on a PUSCH resource scheduled by an RAR,        which corresponds to an RA procedure initiated as part of the        SpCell LBT failure recovery procedure), the network may signal a        positive response via a PDCCH addressed to C-RNTI (that contains        an UL grant for new transmission) while the        ra-ContentionResolutionTimer as described in Citation 5 is        running. In this case, the ra-ContentionResolutionTimer is        started in the first symbol after the Msg 3 transmission        carrying the MAC CE as described in Citation 5.

The following is an example BWP operation according to an exampleimplementation of the present application.

Bandwidth Part Operation In addition to clause 12 of TS 38.213 asdescribed in Citation 7, this subclause specifies requirements on BWPoperation. A Serving Cell may be configured with one or multiple BWPs,and the maximum number of BWP per Serving Cell is specified in TS 38.213as described in Citation 7. The BWP switching for a Serving Cell is usedto activate an inactive BWP and deactivate an active BWP at a time. TheBWP switching is controlled by the PDCCH indicating a downlinkassignment or an uplink grant, by the bwp-InactivityTimer, by RRCsignaling, or by the MAC entity itself upon initiation of Random Accessprocedure. Upon RRC (re-)configuration of firstActiveDownlinkBWP-Idand/or firstActiveUplinkBWP-Id for SpCell or activation of an SCell, theDL BWP and/or UL BWP indicated by firstActiveDownlinkBWP-Id and/orfirstActiveUplinkBWP-Id respectively (as specified in TS 38.331 asdescribed in Citation 3) is active without receiving PDCCH indicating adownlink assignment or an uplink grant. The active BWP for a ServingCell is indicated by either RRC or PDCCH (as specified in TS 38.213 asdescribed in Citation 7). For unpaired spectrum, a DL BWP is paired witha UL BWP, and BWP switching is common for both UL and DL. For eachactivated Serving Cell configured with a BWP, the MAC entity shall: 1>if a BWP is activated:  2>transmit on UL-SCH on the BWP  2>transmit onRACH on the BWP, if PRACH occasions are configured;  2>monitor the PDCCHon the BWP;  2>transmit PUCCH on the BWP, if configured;  2>receiveDL-SCH on the BWP;  2>if the BWP is activated after SpCell LBTfailure-initiated BWP switching: 3> (re-)initialize any suspendedconfigured uplink grants of configured grant Type 1 on the active BWPaccording to the stored configuration, if any, and to start in thesymbol according to rules in subclause 5.8.2. after the RA procedureinitiated as part of SpCell LBT failure has been finished or stopped; 3>report CSI for the BWP after the RA procedure initiated as part ofSpCell LBT failure has been finished or stopped; 3> transmit SRS on theBWP, if configured, after the RA procedure initiated as part of SpCellLBT failure has been finished or stopped;  2> else 3> (re-)initializeany suspended configured uplink grants of configured grant Type 1 on theactive BWP according to the stored configuration, if any, and to startin the symbol according to rules in subclause 5.8.2 3> report CSI forthe BWP 3> transmit SRS on the BWP, if configured.

FIG. 9 is a block diagram illustrating a node for wirelesscommunication, according to various aspects of the present disclosure.As illustrated in FIG. 9, a node 900 may include a transceiver 920, aprocessor 928, a memory 934, one or more presentation components 938,and at least one antenna 936. The node 900 may also include a radiofrequency (RF) spectrum band module, a BS communications module, anetwork communications module, and a system communications managementmodule, Input/Output (I/O) ports, I/O components, and a power supply(not illustrated in FIG. 9).

Each of the components may directly or indirectly communicate with eachother over one or more buses 940. The node 900 may be a UE or a BS thatperforms various functions disclosed with reference to FIGS. 1 through8.

The transceiver 920 has a transmitter 922 (e.g.,transmitting/transmission circuitry) and a receiver 924 (e.g.,receiving/reception circuitry) and may be configured to transmit and/orreceive time and/or frequency resource partitioning information. Thetransceiver 920 may be configured to transmit in different types ofsubframes and slots including but not limited to usable, non-usable andflexibly usable subframes and slot formats. The transceiver 920 may beconfigured to receive data and control channels.

The node 900 may include a variety of computer-readable media.Computer-readable media may be any available media that may be accessedby the node 900 and include both volatile and non-volatile media, andremovable and non-removable media.

The computer-readable media may include computer storage media andcommunication media. Computer storage media may include both volatileand non-volatile media, and removable and non-removable mediaimplemented in any method or technology for storage of information suchas computer-readable instructions, data structures, program modules ordata.

Computer storage media may include RAM, ROM, EPROM, EEPROM, flash memoryor other memory technology, CD-ROM, Digital Versatile Disks (DVD) orother optical disk storage, magnetic cassettes, magnetic tape, magneticdisk storage or other magnetic storage devices. Computer storage mediamay not include a propagated data signal. Communication media maytypically embody computer-readable instructions, data structures,program modules or other data in a modulated data signal such as acarrier wave or other transport mechanism and include any informationdelivery media.

The term “modulated data signal” means a signal that has one or more ofits characteristics set or changed in such a manner as to encodeinformation in the signal. Communication media may include wired mediasuch as a wired network or direct-wired connection, and wireless mediasuch as acoustic, RF, infrared and other wireless media. Combinations ofany of the previously listed components should also be included withinthe scope of computer-readable media.

The memory 934 may include computer-storage media in the form ofvolatile and/or non-volatile memory. The memory 934 may be removable,non-removable, or a combination thereof. Example memory may includesolid-state memory, hard drives, optical-disc drives, etc. Asillustrated in FIG. 9, the memory 934 may store computer-readable,computer-executable instructions 932 (e.g., software codes) that areconfigured to cause the processor 928 to perform various functionsdisclosed herein, for example, with reference to FIGS. 1 through 8.Alternatively, the instructions 932 may not be directly executable bythe processor 928 but be configured to cause the node 900 (e.g., whencompiled and executed) to perform various functions disclosed herein.

The processor 928 (e.g., having processing circuitry) may include anintelligent hardware device, e.g., a Central Processing Unit (CPU), amicro-controller, an ASIC, etc. The processor 928 may include memory.The processor 928 may process the data 930 and the instructions 932received from the memory 934, and information transmitted and receivedvia the transceiver 920, the baseband communications module, and/or thenetwork communications module. The processor 928 may also processinformation to be sent to the transceiver 920 for transmission via theantenna 936 to the network communications module for transmission to acore network.

One or more presentation components 938 may present data indications toa person or another device. Examples of presentation components 938 mayinclude a display device, a speaker, a printing component, and avibrating component, etc.

In various implementations of the present disclosure, the CC may bePCell, PSCell, and/or SCell.

In various implementations of the present disclosure, the SpCell mayinclude PCell and PSCell.

In various implementations of the present disclosure, the UL resourcemay be PRACH resource, PUCCH resource, and/or PUSCH resource. The ULresource may be scheduled by dynamic grant (e.g., via PDCCH) and/orconfigured by RRC (e.g., type 1/type 2 configured UL grant orpre-configured in RRC configuration). When a beam failure (of anSCell(s)) is detected, the UE may trigger a BFR procedure (for anSCell(s)).

In various implementations of the present disclosure, the MAC entity maybe referred to the UE.

In various implementations of the present disclosure, intra-UEprioritization may be needed by a UE if two or more UL resources(scheduled/configured in the same serving cell) overlap in the timedomain. As a result of intra-UE prioritization, the UE may select one ofthe overlapping UL resources for transmission. The selected UL resourcemay be referred to as a prioritized UL resource, and the MAC PDU/TB tobe transmitted on the UL resource may be referred to as a prioritizedMAC PDU/TB. In contrast, the UL resource(s) that is not selected may bereferred to as a deprioritized UL resource(s), and the MAC PDU(s)/TB(s)to be transmitted on the deprioritized UL resource(s) may be referred toas a deprioritized MAC PDU(s)/TB(s).

In various implementations of the present disclosure, the overlap of theresource may mean partially overlap and/or fully overlap.

In various implementations of the present disclosure, the configuredgrant configuration may be (but is not limited to) configured grant Type1 or configured grant Type 2.

In various implementations of the present disclosure, there are twotypes of transmission without dynamic grant: configured grant Type 1where an uplink grant is provided by RRC, and stored as configureduplink grant; and configured grant Type 2 where an uplink grant isprovided by PDCCH, and stored or cleared as configured uplink grantbased on L1 signaling indicating configured uplink grant activation ordeactivation.

In various implementations of the present disclosure, an SpCell mayinclude PCell and PSCell.

In various implementations of the present disclosure, a UL resource maybe a PRACH resource, a PUCCH resource, and/or a PUSCH resource. The ULresource may be scheduled by dynamic grant (e.g., via PDCCH) and/orconfigured by RRC (e.g., type 1/type 2 configured UL grant orpre-configured in RRC configuration).

In various implementations of the present disclosure, a MAC entity (orHARQ entity) may be referred to the UE.

In various implementations of the present disclosure, a PCell LBTrecovery procedure and/or a PSCell LBT recovery procedure may also betermed as a SpCell LBT recovery procedure.

In view of the disclosure, it is obvious that various techniques may beused for implementing the concepts in the present disclosure withoutdeparting from the scope of those concepts. Moreover, while the conceptshave been disclosed with specific reference to certain implementations,a person of ordinary skill in the art may recognize that changes may bemade in form and detail without departing from the scope of thoseconcepts. As such, the disclosed implementations are to be considered inall respects as illustrative and not restrictive. It should also beunderstood that the present disclosure is not limited to the particularimplementations disclosed and many rearrangements, modifications, andsubstitutions are possible without departing from the scope of thepresent disclosure.

What is claimed is:
 1. A user equipment (UE) comprising: one or morenon-transitory computer-readable media containing computer-executableinstructions embodied therein; and at least one processor coupled to theone or more non-transitory computer-readable media, the at least oneprocessor configured to execute the computer-executable instructions to:receive a dynamic grant for scheduling a first uplink (UL) resource;determine whether to obtain a first Medium Access Control (MAC) protocoldata unit (PDU) for transmission using the first UL resource or totransmit a second MAC PDU before obtaining the first MAC PDU; andtransmit the second MAC PDU using the first UL resource if the first ULresource is suitable for transmitting the second MAC PDU.
 2. The UE ofclaim 1, wherein, if the first UL resource is not suitable fortransmitting the second MAC PDU and if the first UL resource isindicated for a new transmission, obtaining the first MAC PDU comprisesgenerating the first MAC PDU for the new transmission using the first ULresource.
 3. The UE of claim 1, wherein, if the first UL resource is notsuitable for transmitting the second MAC PDU and if the first ULresource is indicated for a retransmission, obtaining the first MAC PDUcomprises retrieving the first MAC PDU from a hybrid automatic repeatrequest (HARQ) buffer associated with a HARQ process of the first ULresource for the retransmission using the first UL resource.
 4. The UEof claim 1, wherein the first UL resource is suitable for transmittingthe second MAC PDU if at least one of the following conditions issatisfied: the second MAC PDU is generated for transmission using asecond UL resource scheduled by the dynamic grant; the second ULresource is indicated for a new transmission; the second UL resource isbefore the first UL resource in a time domain; the size of the first ULresource is equal to or greater than the size of the second UL resource;the second MAC PDU is not transmitted successfully on the second ULresource due to a UL Listen-Before-Talk (LBT) failure; and the second ULresource associated with a second hybrid automatic repeat request (HARQ)process identifier (ID) is different from a first HARQ ID associatedwith the first UL resource.
 5. The UE of claim 4, wherein the second MACPDU is stored in a HARQ buffer after being generated, and the HARQbuffer is associated with a HARQ process of the second UL resource. 6.The UE of claim 5, wherein the at least one processor is furtherconfigured to execute the computer-executable instructions to: obtainthe second MAC PDU from the HARQ buffer for transmission using the firstUL resource.
 7. The UE of claim 1, wherein the dynamic grant furtherschedules a second UL resource, the first UL resource is immediatelyafter the second UL resource in a time domain.
 8. The UE of claim 7,wherein the first UL resource and the second UL resource are physicaluplink shared channel (PUSCH) resources.
 9. The UE of claim 7, wherein asize of the first UL resource is equal to or greater than a size of thesecond UL resource.
 10. The UE of claim 1, wherein the dynamic grant isreceived in downlink control information (DCI).
 11. A method performedby a user equipment (UE), the method comprising: receiving a dynamicgrant for scheduling a first uplink (UL) resource; determining whetherto obtain a first Medium Access Control (MAC) protocol data unit (PDU)for transmission using the first UL resource or to transmit a second MACPDU before obtaining the first MAC PDU; and transmitting the second MACPDU using the first UL resource if the first UL resource is suitable fortransmitting the second MAC PDU.
 12. The method of claim 11, wherein, ifthe first UL resource is not suitable for transmitting the second MACPDU and if the first UL resource is indicated for a new transmission,obtaining the first MAC PDU comprises generating the first MAC PDU forthe new transmission using the first UL resource.
 13. The method ofclaim 11, wherein, if the first UL resource is not suitable fortransmitting the second MAC PDU and if the first UL resource isindicated for a retransmission, obtaining the first MAC PDU comprisesretrieving the first MAC PDU from a hybrid automatic repeat request(HARQ) buffer associated with a HARQ process of the first UL resourcefor the retransmission using the first UL resource.
 14. The method ofclaim 11, wherein the first UL resource is suitable for the transmissionof the second MAC PDU if at least one of the following conditions issatisfied: the second MAC PDU is generated for transmission using asecond UL resource scheduled by the dynamic grant; the second ULresource is indicated for a new transmission; the second UL resource isbefore the first UL resource in a time domain; the size of the first ULresource is equal to or greater than the size of the second UL resource;the second MAC PDU is not transmitted successfully on the second ULresource due to a UL Listen-Before-Talk (LBT) failure; and the second ULresource associated with a second hybrid automatic repeat request (HARQ)process identifier (ID) is different from a first HARQ ID associatedwith the first UL resource.
 15. The method of claim 14, wherein thesecond MAC PDU is stored in a HARQ buffer after being generated, and theHARQ buffer is associated with a HARQ process of the second UL resource.16. The method of claim 15, further comprising: obtaining the second MACPDU from the HARQ buffer for transmission using the first UL resource.17. The method of claim 11, wherein the dynamic grant further schedulesa second UL resource, the first UL resource is immediately after thesecond UL resource in a time domain.
 18. The method of claim 17, whereinthe first UL resource and the second UL resource are physical uplinkshared channel (PUSCH) resources.
 19. The method of claim 17, wherein asize of the first UL resource is equal to or greater than a size of thesecond UL resource.
 20. The method of claim 11, wherein the dynamicgrant is received in downlink control information (DCI).